Tube-BOZ

Tyimo · 5th June 2005, 07:16 AM

Hi!

I read in the BOZ article that :
"...I did not find it practical to build a single gain stage tube amplifier, but the relaxed conditions under which a preamp functions makes a tube version of this circuit workable. Simply adjust the voltage and bias values for a tube instead of the MOSFET we will use here...."

Well, could somebody help me how to calculate the voltage and bias values for a Tube-BOZ? I would use E88CC tube with the original 60V PSU, if it is possible. So I could compare the 2 different version, which would give nicer sound, etc.

Thanks!

Tyimo

Netlist · 5th June 2005, 04:58 PM

You might make it more attractive by posting a little schematic.
People here like eye candy you see.

/Hugo

Tyimo · 10th June 2005, 05:34 PM

O.K. Hugo!

Here is your eye candy :-)

(The whole article is on the passdiy site, if somebody wouldn't know it.)

Greets:

Tyimo

Nelson Pass · 10th June 2005, 05:55 PM

From the E88CC curves, it looks offhand like you could run it
at 10 mA with a grounded Grid at 60 volts or so. Probably
1-10 ohms Cathode to ground, and maybe 200-500 ohms
Plate resistance.

Tyimo · 11th June 2005, 03:10 PM

Thank you Mr. Pass!!

moe29 · 11th June 2005, 09:58 PM

If you can, post a schematic drawn for the tube operation.

...would be neat to see.

good luck!

GRollins · 15th June 2005, 02:21 AM

Although it's tempting to compare the solid state version with a tube version using the same rail voltage, I think you'll find that 60V is a little on the low side for tubes. It will work (I've seen people run tubes on rails as low as 15V), but the comparatively low B+ (you'll probably end up with around 30V at the plate) will give you higher distortion. It could be a really nice-sounding preamp, but it wouldn't be fair to compare it directly to the MOSFET version.
As an engineering exercise or just for fun, I'd say go for it. If you want it to sound better, stretch things out a bit more. Yes, that will require a separate power supply, or possibly a single, more complex one. An ordinary 1:1 isolation transformer is just dandy for a 165V rail. That would be a cheap and easy way to give the tube a higher rail without having to drop a lot of money. Use 1N4007s for the bridge; everybody has a few of those gathering dust. If money is real tight, you could use the caps out of a disposable camera. They're free and good for around 300V, well over the requirements you'd need for this circuit. Then, let's say...oh, I dunno, something like a 100 to 1k resistor to make a CRC filter.
Tinker with it a bit. It'll be fun.

Grey

5th June 2005, 07:16 AM	#1
Tyimo diyAudio Member Join Date: Nov 2002 Location: Hungary	Tube-BOZ Hi! I read in the BOZ article that : "...I did not find it practical to build a single gain stage tube amplifier, but the relaxed conditions under which a preamp functions makes a tube version of this circuit workable. Simply adjust the voltage and bias values for a tube instead of the MOSFET we will use here...." Well, could somebody help me how to calculate the voltage and bias values for a Tube-BOZ? I would use E88CC tube with the original 60V PSU, if it is possible. So I could compare the 2 different version, which would give nicer sound, etc. Thanks! Tyimo

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5th June 2005, 04:58 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	You might make it more attractive by posting a little schematic. People here like eye candy you see. /Hugo

10th June 2005, 05:55 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	From the E88CC curves, it looks offhand like you could run it at 10 mA with a grounded Grid at 60 volts or so. Probably 1-10 ohms Cathode to ground, and maybe 200-500 ohms Plate resistance.

11th June 2005, 03:10 PM	#5
Tyimo diyAudio Member Join Date: Nov 2002 Location: Hungary	Thank you Mr. Pass!!

11th June 2005, 09:58 PM	#6
moe29 diyAudio Member Join Date: Dec 2002 Location: Florida	If you can, post a schematic drawn for the tube operation. ...would be neat to see. good luck!

15th June 2005, 02:21 AM	#7
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	Although it's tempting to compare the solid state version with a tube version using the same rail voltage, I think you'll find that 60V is a little on the low side for tubes. It will work (I've seen people run tubes on rails as low as 15V), but the comparatively low B+ (you'll probably end up with around 30V at the plate) will give you higher distortion. It could be a really nice-sounding preamp, but it wouldn't be fair to compare it directly to the MOSFET version. As an engineering exercise or just for fun, I'd say go for it. If you want it to sound better, stretch things out a bit more. Yes, that will require a separate power supply, or possibly a single, more complex one. An ordinary 1:1 isolation transformer is just dandy for a 165V rail. That would be a cheap and easy way to give the tube a higher rail without having to drop a lot of money. Use 1N4007s for the bridge; everybody has a few of those gathering dust. If money is real tight, you could use the caps out of a disposable camera. They're free and good for around 300V, well over the requirements you'd need for this circuit. Then, let's say...oh, I dunno, something like a 100 to 1k resistor to make a CRC filter. Tinker with it a bit. It'll be fun. Grey

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